The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines draw air into an intake manifold through an air intake. The air is mixed with fuel to form an air-and-fuel (A/F) mixture. The A/F mixture is combusted within cylinders to drive pistons, which rotatably turn a crankshaft to produce drive torque.
The A/F mixture in a particular cylinder may combust at an undesired time. More specifically, temperature and/or pressure of the A/F mixture may exceed a critical level. Exceeding the critical temperature and/or pressure may cause the A/F mixture to ignite automatically prior to spark from a spark plug (i.e. a desired timing). The automatic ignition of the A/F mixture at the undesired time may be called “pre-ignition.”
Engine pre-ignition may result in engine knock. For example, engine knock may be a vibration resulting from a rapid increase in cylinder pressure. Engine knock over a sustained period of time may result in, for example, damage to pistons, cylinder rings, and/or exhaust valves. Furthermore, engine knock may increase noise/vibration/harshness (NVH).
Engine control systems may include misfire detection systems and/or knock detection systems that determine if and when an engine knocks. Therefore, engine control systems may regulate engine operation to reduce or prevent engine knock. Preventing engine knock may improve engine performance and/or vehicle drivability.